Question

Cystic fibrosis (CF) is an autosomal recessive disease. In a South American country, a study was conducted to test the hypothesis that cystic fibrosis carriers were less likely to be affected and die from by tuberculosis (TB) infection. To begin the quantitative study, researchers needed to identify the number of individuals in the population that were carriers, knowing the frequency of the cystic fibrosis allele was 0.1 in the population. After their analysis, the researchers concluded that there was evidence to support their hypothesis.

Q8.1 hypothesis

2 Points

The researchers’ hypothesis is based in what larger biological idea?

A. stabilizing selection

B. homeostasis

C. genetic drift

D. codominance

E. balancing selection

F. the competitive exclusion principle

Q8.2

The researchers determined ___% of the population to be cystic fibrosis carriers.

Answer 1

Q8.1

E. balancing selection

In the study, the hypothesis was that the presence of the Cystic Fibrosis causing allele will prevent Tuberculosis from developing. As per this hypothesis, the prevalence of Tuberculosis in this population will protect the Cystic Fibrosis allele from Negative selection, which results in Balancing selection. In other word, the positive selection for this allele due to its positive effect on Tuberculosis survival balances the negative selection due to Cystic Fibrosis.

Q8.2)

The frequency of the CF causing allele = 0.1

=> Frequency of Wild Type allele = 1 - 0.1 = 0.9

=> Frequency of Heterozygotes = 2 * 0.1 * 0.9 = 0.18